The present invention focuses on the development of a control device in a vehicle electrical system, which controls the flow of energy between a generator, various electrical loads, and stored energy sources in a vehicle.
A vehicle electrical system is generally comprised of a generator, electrical loads comprising a multitude of electrical and/or electromechanical devices, and stored energy sources, such as batteries, which provide electrical energy when the generator is not operating.
A common problem in electrical systems that employ a stored energy source such as a battery is gradual dissipation of the stored energy via leakage associated with devices that remain connected to the electrical circuit. The accumulation of such leakage in the electrical system over an extended period depletes the stored energy source. Accordingly, there is a need for a control device that protects the stored energy sources from the detrimental effect of electrical leakage.
Environmental conditions also aggravate energy dissipation from stored energy devices. Rain, humidity, and condensation promote dendrite growth between surfaces of opposite polarity that eventually develops into a short circuit. This can happen in any electronic circuit that is not hermetically sealed. Consequently, there is a need for a control device that disconnects the electrical system from the loads to reduce the incidence of moisture related dendrite growth in electronic circuits.
As a safety measure, vehicle maintenance personnel routinely disconnect the battery from the vehicle electrical systems during electrical service. Manual battery disconnection is time consuming and poses a risk of accidental arcing and subsequent misconnection of the leads when the circuit is restored. Therefore, there is a need for a load and battery charge device which is capable of disconnecting the battery and other stored energy sources from the vehicle electrical systems without requiring physical removal of battery cables.
Advances in vehicle electrical system technology have led to the incorporation of various intelligent controller-based devices in the electrical system. Such devices normally incorporate boot-up procedures that involve initializing certain parameters at vehicle start-up time. These parameters are stored in the memory of such controllers even when the vehicle's engine is turned off. So long as the stored energy sources are connected to the electrical system, the devices retain the parameters uploaded during boot-up procedure. In particular, some boot-up procedures implement time delays to inhibit certain operating conditions. For example, some controller-based engine starters inhibit engine cranking for a period of time during which the engine's temperature is raised via heating elements. It would be undesirable if the stored energy sources were disconnected from the vehicle electrical system before such time delays have expired. Accordingly, there is a need for a control device capable of accommodating time delays during certain operating sequences and before disconnecting the stored energy sources from the electrical system.
Under some operating conditions the generator in a vehicle electrical system may provide electrical energy in excess of the system load requirement. Such energy may be used to power auxiliary circuits and devices that are not a part of the primary vehicle electrical system. This is normally accommodated by the use of a dedicated auxiliary output port. Although, the excess energy is available, it would be undesirable to allow such devices to consume energy beyond the capability of the generator since it would deprive the primary system loads of their energy requirement and may cause the primary system voltage to drop to the point of disabling normal operation. Therefore, there is a need for a control device that can provide controllably limited energy to auxiliary output ports.
There are circumstances where it is necessary for the vehicle operator to know the charge status of the stored energy source. For example, a vehicle operator who is uninformed about a discharged battery in the system may shut down the vehicle engine and face a serious problem of not having enough energy to restart the engine. It is also desirable to have a means to predict when a battery needs to be replaced before its actual failure. By providing battery charge status and battery health information to the operator the situations that lead to an electrically disabled vehicle may be avoided. Accordingly, there is a need for a control device that is capable of providing status information concerning the battery state of charge and battery health.
In yet other applications, certain devices in the electrical system need to be constantly connected to an energy source. For example, emergency flashers need to be capable of activation even though the engine is not operating. Accordingly, there is a need for a control device that is capable of detecting device-specific load conditions to remain capable of activation despite battery disconnection from the main vehicle loads.